1. Field of the Invention
The present invention relates to baggage inspection systems. More particularly, it relates to container, e.g., baggage, inspection systems and methods for detecting security threats.
2. Discussion of Related Art
Security checkpoints, such as those located in airports, screen people and packages for contraband, such as weapons or explosives. Various technologies are used at such checkpoints. Typically, individuals pass through metal detection devices. Projection x-ray systems screen baggage and packages. In current conditions of heightened security, passengers can experience long delays in passing through security checkpoints. For baggage, an operator typically reviews all images of screened baggage to determine whether the baggage includes contraband. A typical operator receives extensive training to recognize certain types of objects in an x-ray image. Furthermore, a typical operator receives training to distinguish objects layered within the bags from a single two dimensional x-ray image.
Projection x-ray systems were designed to provide high-resolution images for the detection of guns and knives. Despite such imaging, the individuals using conventional projection x-ray systems to perform screening in certain circumstances do not detect forbidden objects. Specifically, projection x-ray scanners are not designed to detect explosives. Therefore, it is difficult for even the most highly trained screener to detect explosives using projection x-ray technology. There is currently no mandate to use explosive detection systems (EDS) to screen carry-on baggage. However, a need remains for a system that can detect explosives in carry-on baggage, especially for carry-on baggage of selected individuals (e.g., Computer Assisted Passenger Profiling System (CAPPS) selectees).
In addition to individuals and carry-on baggage, checked bags are also now scanned at airports. Generally, in the United States, the Transportation Security Administration (TSA) uses computed tomography (CT) scanning for checked bags. CT scanners create a three dimensional image of a bag which allows better differentiation of objects relative to projection x-ray systems. Explosive detection system designers specifically developed and deployed CT scanners for the detection of explosives. Conventional CT scanners do not provide a high-resolution dual energy projection x-ray image useful for detecting weapons. For this reason among others, the TSA has not used CT scanners for carry-on baggage or security checkpoints.
As noted above, CT technology is effective for explosive detection. CT machines typically incorporate a rotating ring or “gantry” on which the X-ray source and detectors are mounted. FIG. 1 is a cross sectional view of a conventional CT scanner 10. The CT scanner 10 includes a gantry 11 surrounding a tunnel 20. A conveyor (not shown) moves baggage through the tunnel 20 for scanning. The gantry 11 rotates about the tunnel, producing one slice of data for each rotation. An x-ray source 30 produces a narrow angle beam 40. A detector 31 is positioned on the gantry 11 to intersect the x-ray beam 40 passing through the tunnel. The detector 31 may consist of multiple detectors, which typically are located equal distances from the x-ray source. The x-ray source 30 and detector 31 must be sized and positioned so that the entire tunnel falls within the x-ray beam. The data from the detector is analyzed using a computer to generate a three-dimensional representation of the contents of the baggage being scanned.
Conventional CT scanning and reconstruction used in baggage inspection is slow and cumbersome. There are two known methods for CT scanning, i.e., helical and start/stop. In helical scanning, an object under inspection, e.g., a bag, is continuously moved through the scanner. The bag has to be moved slowly so that each rotation of the gantry is substantially in a single plane. In start/stop scanning, the bag is periodically stopped and a single slice is scanned. The bag is then moved a short distance, stopped and scanned again. Both of these processes result in slow movement of baggage through the scanner. Once the data has been collected, the data is reconstructed to create a three dimensional representation of the baggage. From the three dimensional representation, individual items are reviewed as possible threats. The three dimensional representation, or slices of it, may also be displayed for review by an operator.
A need remains for systems and methods that provide a higher throughput relative to conventional CT systems.
Furthermore, The TSA has recognized the need to improve the security process at the passenger checkpoint, as evidenced by a recent TSA request for proposals for checkpoint EDS. Simply replacing the existing checkpoint X-ray systems with EDS will be an expensive proposition. It is currently driven by the need to improve the detection performance at the checkpoint. Adding additional benefits such as increased throughput and labor reduction will provide incentive for other stakeholders to support the capital investment.
Adding special selectee lanes to existing passenger checkpoints would help with throughput but limits the ability of TSA or an airport to respond to changes in the threat condition or an increase in the percentage of CAPPS selectees. In addition, forcing only selected passengers to the selectee lane alerts any potential terrorist of his or her status while also alerting the traveling public to their special selectee status. This alert can cause additional problems for TSA based on perceived discriminatory practices.
TSA and airports are struggling to keep up with passenger loads using today's passenger screening systems and procedures. Lines up to 2 hours can form during peak periods and will likely get worse as TSA headcount is further rationalized and passenger loads increase. Adding additional screening lanes can cost millions and take months. Airlines and airports would eagerly embrace a system that can significantly increase the throughput of the passenger checkpoint as a means to improve passenger service while maintaining or increasing detection performance.